Whats the difference between 2.5" and 3" exhausts?

[cctman]

I'm about to finish up my stage 2 to stage 3 move. Before I grab a DP and exhaust I want to make sure I understand the details and differences between the different sizes.

 

[rodmoe]

IT has been stated by many people you won't NEED a 3 inch cbe unless you are planning to go big turbo at some point down the road if not the a 2.5 will fit the bill very well and flow all you need to.. or so I am told ..

 

[no-pistons]

1/2"

 

[cctman]

IT has been stated by many people you won't NEED a 3 inch cbe unless you are planning to go big turbo at some point down the road if not the a 2.5 will fit the bill very well and flow all you need to.. or so I am told ..

Thats good to know... but I think what I'm looking for would be something like... a 2.5" pipes generally preserve more torque and hp on stock fiesta st turbos, but 3" pipe allows for more hp gains at higher levels and quicker turbo spooling off low RPMs.

Now of course I made this up this may not be true, but I'm looking for a more direct comparison with anyone who has experience with both.

 

[Sirsinclair]

Thats good to know... but I think what I'm looking for would be something like... a 2.5" pipes generally preserve more torque and hp on stock fiesta st turbos, but 3" pipe allows for more hp gains at higher levels and quicker turbo spooling off low RPMs.

Now of course I made this up this may not be true, but I'm looking for a more direct comparison with anyone who has experience with both.

Well I have stage 3 with a 3" exhaust and I'm getting pro tuned by COBB, it might give an answer to that question. Problem is... They are booked out pretty far and my appointment isn't until Aug. 12th.

 

[D1JL]

1/2"

I was going to say that.

With a forced induction engine the size of the exhaust is inconsequential as long as the flow is sufficient as pointed out by rodmoe.
As I do have a 3 inch system, I can tell you that the main difference is the tone.




Dave

 

[cctman]

I was going to say that.

With a forced induction engine the size of the exhaust is inconsequential as long as the flow is sufficient as pointed out by rodmoe.
As I do have a 3 inch system, I can tell you that the main difference is the tone.




Dave

So tone as in the larger 3" exhaust has a more low end grunt to it?

 

[BoostBumps]

1/2"

good one! LOL

 

[DHM1]

1/2"

man I was hoping someone didn't beat me to it! haha

Russ

 

[D1JL]

So tone as in the larger 3" exhaust has a more low end grunt to it?

Yes,
It has a lower pitch.
More throaty.



Dave

 

[mouse]

I'm in this same dilemma, but I'm going to straight pipe it all the way plus add a 2JR decatted downpipe. I haven't seen any scientific explanation, dyno comparisons, or tests as to why either one is better than the other when it comes to the Fiesta ST.

 

[JPGC]

I'm running a modified MBRP 3" cat-back as well as a modified downpipe. Both are now truly 3"...With my Stg3/ Freektune setup, I feel no butt-dyno difference with the 3", though my tune isn't optimized for the 3" exhaust yet. In all reality, with the stock turbo in place, I don't think there will be much, if any, gain. Beyond stg3 (turbo upgrade, etc) is where you would start to see results.